Agricultural harvester with propulsion load shifting between dual engines

ABSTRACT

An agricultural harvester includes a first power unit which is couplable with a first primary load. The first primary load includes a threshing system load. A second power unit has a threshold power output and is couplable with a second primary load. The second primary load includes a propulsion load. A first motor/generator is mechanically coupled with the first power unit. A second motor/generator is mechanically coupled with the second power unit. The second motor/generator and the first motor/generator are electrically coupled together. At least one electrical processing circuit is coupled with each of the first motor/generator and the second motor/generator. The at least one electrical processing circuit is configured for selectively transferring electrical power from the first motor/generator to the second motor/generator, when the second power unit is at or above the threshold power output.

FIELD OF THE INVENTION

The present invention relates to work machines, and, more particularly,to work machines including an internal combustion engine which may beused to drive primary and external loads.

BACKGROUND OF THE INVENTION

A work machine, such as a construction work machine, an agriculturalwork machine or a forestry work machine, typically includes a power unitin the form of an internal combustion (IC) engine. The IC engine mayeither be in the form of a compression ignition engine (i.e., dieselengine) or a spark ignition engine (i.e., gasoline engine). For mostheavy work machines, the power unit is in the form of a diesel enginehaving better lugging, pull-down and torque characteristics forassociated work operations.

The step load response of an IC engine in transient after a load impactis a feature mostly influenced by the engine displacement, the hardwareof the engine (e.g., whether it has a standard turbocharger, aturbocharger with waste gate or variable geometry, etc.), and by thesoftware strategy for driving the air and fuel actuators (e.g., exhaustgas recirculation, turbocharger with variable geometry turbine (VGT),fuel injector configuration, etc.) with respect to the requirements ofemissions legislation (e.g., visible smoke, nitrous oxides (NOx), etc.),noise or vibrations. The load impact may be the result of a drivetrainload (e.g., an implement towed behind the work machine) or an externalload (i.e., a non-drivetrain load). External loads can be classified asincluding both parasitic and auxiliary loads. Parasitic loads arenon-drivetrain loads placed upon an engine through normal operation ofthe work machine, without operator intervention (e.g., an engine coolingfan, hydraulic oil cooling circuit pump, etc.). Auxiliary loads arenon-drivetrain loads placed upon an engine through selective operatorintervention (e.g., an auxiliary hydraulic load such as an unloadingauger on a combine, a front end loader, a backhoe attachment, etc.)

Engine systems as a whole react in a linear manner during theapplication of a transient load. Initially, the load is applied to thedrive shaft of the IC engine. The IC engine speed decreases when theload increases. The engine speed drop is influenced by whether thegovernor is isochronous or has a speed droop. The air flow is increasedto provide additional air to the IC engine by modifying the airactuators. A time delay is necessary to achieve the new air flow setpoint. The fuel injection quantity, which is nearly immediate, isincreased with respect to both the smoke limit and maximum allowablefuel quantity. The engine then recovers to the engine speed set point.The parameters associated with an engine step load response in transientafter a load impact are the speed drop and the time to recover to theengine set point.

An IC engine may be coupled with an infinitely variable transmission(IVT) which provides continuous variable output speed from 0 to maximumin a stepless fashion. An IVT typically includes hydrostatic andmechanical gearing components. The hydrostatic components convertrotating shaft power to hydraulic flow and vice versa. The power flowthrough an IVT can be through the hydrostatic components only, throughthe mechanical components only, or through a combination of bothdepending on the design and output speed.

A work machine including an IC engine coupled with an IVT may exhibitproblems to be overcome in two ways: First, sudden loads placed on thedrivetrain or vehicle hydraulic functions cause the engine speed todecrease. The response time to change the IVT ratio to reduce engineload once decreased is slower than necessary to prevent substantialengine speed drop and sometimes stall. Second, when an external load isapplied to the IC engine, such as when filling the bucket of a front endloader on an IVT vehicle, the operator may command a vehicle speedsubstantially more than what is capable from the IC engine. Under theseconditions the IVT output torque and speed may result in excessive wheelslippage and other undesirable characteristics. Likewise, if an externalload from another external function to the transmission is activated,such as hydraulic functions, the external load combined with thetransmission output capability may place the engine in an overloadcondition.

The demands for increased performance and fuel economy will increasesignificantly for work machines within the next decade. This will becomplicated by the implementation of devices to reduce emissions. Theincreasing size and productivity of work machines is expected to resultin power demand higher than will be available from economical singleinternal combustion engines. This will drive the development of vehiclesusing very large, heavy and expensive industrial engines. The complexityand cost of such engines may be prohibitive and curtail theimplementation of higher capacity machinery.

One method around the problem is to use hybrid electric-IC enginetechnology with a storage battery to supplement the internal combustionengine with electric power boost. This is expected to work very well,but the electric power boost is only available for relatively shortperiods of time. The amount of time available for electric boost isdetermined by the size of the battery. Batteries with enough capacity toprovide sustained levels of power boost will of necessity be large,heavy and costly, thus limiting their practicality.

Another advantage with battery boosted hybrids is the ability to operateelectrical drives with the IC engine shut down. For example, the HVAC,lights, air compressors, cooling fans, grain tank unloading systems,etc., could be operated without the need to start the IC engine. Thelength of time these drives can be operated with the engine off islimited, again, by the size of the battery. Batteries large enough to dosignificant work for extended time periods with the engine off may betoo large, heavy and costly to be practical.

What is needed in the art is a work machine and corresponding method ofoperation providing sustained, increased power capability with many ofthe advantages of electric-IC engine hybrids, while still meetingincreasingly stringent emissions requirements.

SUMMARY OF THE INVENTION

The invention in one form is directed to an agricultural harvester,including a first power unit which is couplable with a first primaryload. The first primary load includes a threshing system load. A secondpower unit has a threshold power output and is couplable with a secondprimary load. The second primary load includes a propulsion load. Afirst motor/generator is mechanically coupled with the first power unit.A second motor/generator is mechanically coupled with the second powerunit. The second motor/generator and the first motor/generator areelectrically coupled together. At least one electrical processingcircuit is coupled with each of the first motor/generator and the secondmotor/generator. The at least one electrical processing circuit isconfigured for selectively transferring electrical power from the firstmotor/generator to the second motor/generator, when the second powerunit is at or above the threshold power output.

The invention in another form is directed to a method of operating anagricultural harvester, including the steps of: driving a threshingsystem load with a first power unit; driving a propulsion load with asecond power unit, the second power unit being mechanically independentfrom the first power unit; driving a first motor/generator with thefirst power unit; driving a second motor/generator with the second powerunit; detecting when the second power unit is at or above a thresholdpower output; and transferring electrical power from the firstmotor/generator to the second motor/generator, dependent upon thedetection of the second power unit at or above the threshold poweroutput.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an embodiment of an agriculturalharvester of the present invention;

FIG. 2 is a schematic illustration of a particular embodiment of anagricultural harvester of the present invention in the form of anagricultural combine; and

FIG. 3 is an embodiment of a method of operation of the agriculturalharvester shown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, there is shown a schematic illustration of anembodiment of an agricultural harvester 10 of the present invention.Agricultural harvester 10 is assumed to be a John Deere agriculturalcombine, but could be a different type of agricultural harvester.

Agricultural harvester 10 includes a first power unit in the form of afirst IC engine 12, and a second power unit in the form of a second ICengine 14. First IC engine 12 has a first drivetrain, typicallyincluding an output crankshaft 16, with a first rated output whichdrives a first primary load 18, and optionally one or more externalloads 20. First primary load 18 is a threshing system load associatedwith one or more of the following: a cutting platform; a header; afeederhousing; a rotor; a separator; and a residue chopper. Firstprimary load 18 preferably is a drivetrain load which is mechanicallydriven by first IC engine 12, but can also be electrically driven by afirst motor/generator 22.

Second IC engine 14 is mechanically independent from first IC engine 12.Second IC engine 14 has a second drivetrain, typically including anoutput crankshaft 24, which drives a second primary load 26, and one ormore external loads 28. Second IC engine 14 has a second rated outputwhich is approximately the same as the first rated output of first ICengine 12. In the embodiment shown, first IC engine 12 and second ICengine 14 are each assumed to have a rated output of 250 kW.

Second primary load 26 is a propulsion load for selectively propellingagricultural harvester 10 across the ground. To that end, an IVT in theform of a hydrostatic transmission may be selectively engaged/disengagedwith crankshaft 24, and provides motive force to one or more drivewheels. Of course, it will be appreciated that in the case of atrack-type work vehicle, crankshaft 24 may be coupled with a groundengaging track. Second primary load 26 preferably is a drivetrain loadwhich is mechanically driven by second IC engine 14, but can also beelectrically driven by a second motor/generator 30.

The one or more external loads 28 may include one or more auxiliaryloads, and may also include one or more parasitic loads. Auxiliary loadsare non-drivetrain hydraulic or electric loads placed upon second ICengine 14 through selective operator intervention (e.g., an auxiliaryhydraulic load such as an unloading auger on a combine, a front endloader, a backhoe attachment, etc.) Parasitic loads are non-drivetrainloads placed upon second IC engine 14 through normal operation of theagricultural harvester, without operator intervention (e.g., anelectrically driven engine cooling fan associated with first IC engine12, etc.). The external loads can be powered from individual electricmotors powered by second motor/generator 30, or can optionally bepowered directly from second motor/generator 30.

In the embodiment shown in FIG. 1, external loads 20 are optional loadsthat can be placed upon first IC engine 12, and all of the externalloads 28 are carried by second IC engine 14. This is because it isanticipated that slug loads carried by first IC engine 12 from thethreshing system may be high, and the external loads are thus shifted tosecond IC engine 14. However, it is possible to split the external loadsbetween first IC engine 12 and second IC engine 14, dependent uponexpected loads, size of the IC engines (which could be the same ordifferent), number of external loads, etc.

First IC engine 12 and second IC engine 14 are each assumed to be adiesel engine in the illustrated embodiment, but could also be agasoline engine, propane engine, etc. IC engines 12 and 14 are sized andconfigured according to the application.

First motor/generator 22 and second motor/generator 30 are electricallycoupled together via power line 32 to pass electrical power back andforth between first motor/generator 22 and second motor/generator 30.When receiving electrical power, the particular motor/generator 22 or 30is operated as a motor to add mechanical power to the output from arespective IC engine 12 or 14, as will be described in more detailbelow.

An electrical processing circuit for controlling operation ofagricultural harvester 10 generally includes a first engine control unit(ECU) 34, a second ECU 36, a vehicle control unit (VCU) 38, and atransmission control unit (TCU) 40. First ECU 34 electronically controlsoperation of first IC engine 12, and is coupled with a plurality ofsensors (not specifically shown) associated with operation of first ICengine 12. For example, ECU 34 may be coupled with a sensor indicatingengine control parameters such as an air flow rate within one or moreintake manifolds, engine speed, fueling rate and/or timing, exhaust gasrecirculation (EGR) rate, turbocharger blade position, etc.Additionally, ECU 34 may receive output signals from VCU 38 representingvehicle control parameters input by an operator, such as a commandedground speed (indicated by a position of the gear shift lever andthrottle and/or hydrostat lever) or a commanded direction ofagricultural harvester 10 (indicated by an angular orientation of thesteering wheel).

Similarly, second ECU 36 electronically controls operation of second ICengine 14. ECU 36 operates in a manner similar to ECU 32 describedabove, and will not be described in further detail. It will also beappreciated that for certain applications, ECU 34 and ECU 36 can becombined into a single controller.

TCU 38 electronically controls operation of the IVT making up secondprimary load 26, and is typically coupled with a plurality of sensors(not shown) associated with operation of the IVT. ECU 34, ECU 36, VCU 38and TCU 40 are coupled together via a bus structure providing two-waydata flow, such as controller area network (CAN) bus 42.

Although the various electronic components such as ECU 34, ECU 36, VCU38 and TCU 40 are shown coupled together using wired connections, itshould also be understood that wireless connections may be used forcertain applications.

Referring now to FIG. 2, a specific embodiment of agricultural harvester10 of the present invention in the form of an agricultural combine willbe described in greater detail. The primary loads driven by first ICengine 12 and second IC engine 14 include two types of drivetrain drivenloads. Namely, first IC engine 12 drives a primary load associated witha threshing system 44, and second IC engine 14 drives a primary loadassociated with a hydrostatic propulsion 46. The threshing system loadsare drivetrain loads associated with one or more of the following: acutting platform; a header; a feederhousing; a rotor; a separator; and aresidue chopper.

The external loads driven by second IC engine 14 include two types ofnon-drivetrain, hydraulic or electrical loads; namely, auxiliary loadscommanded by an operator and parasitic loads not commanded by anoperator. In the embodiment of FIG. 2, the auxiliary loads 48 arenon-drivetrain loads associated with one or more of the following: aheating and air conditioning system; a reel drive; a cleaning shoedrive; an air compressor for cleanout function; a vehicle lightingsystem; a clean grain unloading system; a cleaning fan drive; acutterbar/auger drive; a chaff spreader; a clean grain elevator; and anauxiliary electrical power outlet. All of these auxiliary loads 48(except the lighting system and auxiliary electrical power outlet) areindicated as being electrically driven loads, powered by respectiveelectric motors (each designated “M”, but not specifically numbered).The various motors M are selectively energized using an electricalprocessing circuit 50 (shown schematically in block form), which mayinclude VCU 38, a rectifier and a DC-to-AC inverter. Electricalprocessing circuit 44 electrically couples second motor/generator 46with a motor M associated with a selected auxiliary load 48. Whenproviding electrical power to one or more auxiliary loads 48, it will beappreciated that second motor/generator 30 is operated as amotor/generator with an electric power output. The auxiliary loads canalso include one or more operator initiated hydraulic loads, not shown.

In the event that second IC engine 14 is not operating and electricalpower is required for temporary powering of one or more auxiliary loads48, an electrical storage battery 52 is also coupled with electricalprocessing circuit 50. Of course, a bank of batteries can beelectrically connected together for a higher amp*hour rating. The powerfrom battery 52 can be applied as DC power, or inverted and applied asAC power.

The auxiliary loads 48 can be hardwired to the electrical processingcircuit 50, second motor/generator 30 and/or battery 52, oralternatively may be coupled using modular connectors or plugs (e.g.,one or more of the electrical plug-in outlets shown in FIG. 2). Further,the auxiliary loads 28 may be driven at the same or a differentoperating speed than the first IC engine 12. This allows the externalload functions to be at a different speed than the threshing andpropulsion functions, which can be important for certain operatingconditions such as tougher crop material when approaching dusk, etc.

First motor/generator 22 and second motor/generator 30 are electricallycoupled together, as indicated by electric power line 32. This allowsintelligent power management (IPM) by splitting the power needs betweenfirst IC engine 12 and second IC engine 14. Electric power can betransferred from first motor/generator 22 to second motor/generator 30,or vice versa, depending upon the power needs associated with primaryloads 18 and 26, or auxiliary loads 48.

A primary load in the form of a propulsion load can be a large load onan IC engine. When using dual engines as described above, it would bedesirable to keep each engine as small as possible to improve fuelefficiency. For propulsion loads under most operating conditions, asmaller engine is sufficient to still operate within an efficientoperating range. However, an IC engine which is sized smaller can beoverloaded as a result of a spiked propulsion load, such as may occurwhen traveling up a steep hill, when processing slug crop loads in acombine, etc. The present invention uses dual engines as describedherein to prevent high propulsion loads from overloading second ICengine 14.

Referring now to FIG. 3, a method of operating agricultural harvester 10using IPM with first motor/generator 22 and second motor/generator 30will be described in greater detail. When the harvester 10 is at a fieldfor harvesting operations, first IC engine 12 is used to drive thethreshing system and second IC engine 14 is used to drive the propulsionsystem (blocks 60 and 62). Concurrently, first IC engine 12 is used todrive first motor/generator 22 and second IC engine 14 is used to drivesecond motor/generator 30. The auxiliary loads 48 which are driven bysecond motor/generator 30 in turn add to the load placed on second ICengine 14.

The power output from second IC engine 14 is monitored to assure thatsecond IC engine 14 is not operating at or above a predeterminedthreshold power output (block 64). The largest load on second IC engine14 is from the propulsion load, and thus the monitored power level fromsecond IC engine 14 primarily corresponds to power used to drive thepropulsion load. In one embodiment, the maximum threshold power outputis assumed to be the maximum rated power output of second IC engine 14at a given operating speed. However, the threshold power output can beany predetermined power output from second IC engine 14, such as apercentage of the maximum rated power output at a given operating speed.

If the power output from second IC engine 14 is not above the thresholdpower output, then the control logic simply remains in a wait state(decision block 66 and line 68). On the other hand, if the monitoredpower output from second IC engine 14 is at or above the threshold poweroutput, then power is added to the output drivetrain from second ICengine 14 by transferring electrical power from first motor/generator 22to second motor/generator 30 (decision block 66 and block 70). In otherwords, additional power is added to the drive train from second powerunit 14 by transferring electrical power to second motor/generator 30and operating second motor/generator 30 in a motor mode. The controllogic then repeats until the harvester is turned off (line 72).

It will be appreciated to those familiar in the IC engines arts that themaximum rated output for a given engine changes as the RMP of the enginechanges. At a given operating speed, the rated output is in essence theupper limit on the torque curve for that engine at the given operatingspeed. As the engine speed increases, the rated output typicallylikewise increases, up to the maximum rated operating speed for theengine. The control logic described above uses a threshold power outputwhich is a percentage of the rated power output at a given operatingspeed, such as 80% or 100% of the rated power output. It will also beappreciated that under some operating conditions, it is possible toincrease the engine speed to thereby increase the threshold poweroutput, rather than transfer electrical power to second motor/generator30. In many instances the engine droop and recovery time makes thisoption less desirable, so the control logic above assumes that powerwill be added instead by transferring electrical power to secondmotor/generator 30.

Having described the preferred embodiment, it will become apparent thatvarious modifications can be made without departing from the scope ofthe invention as defined in the accompanying claims.

1. An agricultural harvester, comprising: a first power unit which iscouplable with a first primary load, said first primary load including athreshing system load; a second power unit having a threshold poweroutput above zero, said second power unit being couplable with a secondprimary load, said second primary load including a propulsion load; afirst motor/generator mechanically coupled with said first power unit; asecond motor/generator mechanically coupled with said second power unit,said second motor/generator and said first motor/generator beingelectrically coupled together; and at least one electrical processingcircuit coupled with each of said first motor/generator and said secondmotor/generator, said at least one electrical processing circuit beingconfigured for selectively transferring electrical power from said firstmotor/generator to said second motor/generator, when said second powerunit is one of at and above said threshold power output.
 2. Theagricultural harvester of claim 1, wherein said threshold power outputof said second power unit corresponds to a maximum rated output of saidsecond power unit.
 3. The agricultural harvester of claim 1, whereinsaid at least one electrical processing circuit is configured forselective bidirectional transfer of electrical power between said firstmotor/generator and said second motor/generator.
 4. The agriculturalharvester of claim 1, wherein said first motor/generator is mechanicallyinterconnected between said first power unit and said first primaryload, and said second motor/generator is mechanically interconnectedbetween said second power unit and said second primary load.
 5. Theagricultural harvester of claim 1, wherein said first power unitincludes a first drive train and said second power unit includes asecond drive train, said first primary load being driven by said firstdrive train and said second primary load being driven by said seconddrive train.
 6. The agricultural harvester of claim 1, wherein saidsecond motor/generator is configured to electrically drive at least oneexternal load.
 7. The agricultural harvester of claim 6, wherein eachsaid external load corresponds to one of a parasitic load and anauxiliary load.
 8. The agricultural harvester of claim 7, wherein eachsaid parasitic load is a non-drivetrain load without operatorintervention, and each said auxiliary load is a non-drivetrain load withoperator intervention.
 9. The agricultural harvester of claim 8, whereinsaid agricultural harvester is an agricultural combine, and said atleast one auxiliary load corresponds to at least one of: a heating andair conditioning system; a reel drive; a cleaning shoe drive; an aircompressor for cleanout function; a vehicle lighting system; a cleangrain unloading system; a cleaning fan drive; a cutterbar/auger drive; achaff spreader; a clean grain elevator; and an auxiliary electricalpower outlet.
 10. The agricultural harvester of claim 1, wherein saidagricultural harvester is an agricultural combine, and said threshingsystem load corresponds to at least one of: a cutting platform; aheader; a feederhousing; a rotor; a separator; and a residue chopper.11. The agricultural harvester of claim 1, wherein said first power unitand said second power unit are each an internal combustion (IC) engine.